Does it matter whether you pin them or not? I think I read about an issue specific to pinned tabs, but I can't remember where I saw it or what versions of Firefox were affected.

More generally speaking:

(1) When Firefox starts up and does not automatically display your previous session windows and tabs, could you check the History menu:

(A) If Restore Previous Session is available (not grayed out), select that. Check your startup setting to make sure it isn't set to start with your home page: Startup, home page, tabs, and download settings.

(B) Are any recently closed windows listed that might contain the missing tabs? On the graphical menu, it's below the list of tabs. On the History menu from the menu bar, there's a fly-out list.

(2) Certain privacy settings will prevent Firefox from restoring previous session tabs:

(A) Automatic private browsing (B) Clearing browsing history at shutdown

Please check on the Options page as follows:

"3-bar" menu button (or Tools menu) > Options

In the left column click Privacy. On the right side, there is a selector with three options:

• "Firefox will: Remember history" -- change that to "Firefox will: Use custom settings for history" so you can see individual settings
• "Firefox will: Never remember history" -- change that to "Firefox will: Use custom settings for history" so you can turn off automatic private browsing (uncheck the first box)
• "Firefox will: Use custom settings for history" -- okay

If "Clear history when Firefox closes" is not selected, you're done here.

If "Clear history when Firefox closes" IS selected, click the Settings button to make sure that "Browsing & download history" is not set to be cleared.

Does all of that check out okay?

Try to use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

• "3-bar" menu button > Exit (Power button)
• Windows: File > Exit
• Mac: Firefox > Quit Firefox
• Linux: File > Quit